In the past year, the veteran country-pop singer has played at the Bonnaroo festival and sat in with Phish. Now he's bound for Glastonbury in England, via the Belly Up in Solana Beach.

FILE - This June 14, 2012 file photo shows singer Kenny Rogers performing at the 2012 Songwriters Hall of Fame induction and awards gala at the Marriott Marquis Hotel in New York. The northeast Georgia home owned by country singer Kenny Rogers that was scheduled to be put up for auction has been sold. Grand Estates Auction Co. in Charlotte, N.C., says Rogers sold the house and its 150 acres Wednesday, June 27, for $2.25 million. The property is located near Nicholson, Ga., and included a 5,681-square-foot-house, a 2,675-square foot pool, an 8-acre lake, horse riding trails, go-cart track and other amenities. (Photo by Evan Agostini/Invision, file)
— EVAN AGOSTINI/INVISION/AP

FILE - This June 14, 2012 file photo shows singer Kenny Rogers performing at the 2012 Songwriters Hall of Fame induction and awards gala at the Marriott Marquis Hotel in New York. The northeast Georgia home owned by country singer Kenny Rogers that was scheduled to be put up for auction has been sold. Grand Estates Auction Co. in Charlotte, N.C., says Rogers sold the house and its 150 acres Wednesday, June 27, for $2.25 million. The property is located near Nicholson, Ga., and included a 5,681-square-foot-house, a 2,675-square foot pool, an 8-acre lake, horse riding trails, go-cart track and other amenities. (Photo by Evan Agostini/Invision, file)
/ EVAN AGOSTINI/INVISION/AP

How cool has Kenny Rogers become, against all odds, as he approaches his 75th birthday in August?

Let us count the ways:

This summer, the veteran country-pop vocal star will co-headline at Glastonbury, the tres hip rock, hip-hop and Electronic Dance Music festival in England (which the Coachella Valley Music & Arts Festival in Indio is partly modeled after).

His Glastonbury gig comes a year after he appeared, however improbably. at the 2012 Bonnaroo festival in Tennessee. There, he sat in with top jam band Phish, who enthusiastically backed him as he (and much of the audience) sang his 1978 hit, “The Gambler.”

More improbably, Rogers not only performed a full set with his own band at Bonnaroo (which last year also featured Radiohead, Skrillex and The Roots), he earned some of the best reviews of the four-day festival.

Billboard hailed Rogers as “spellbinding” and “breathtaking,” and credited him for delivering “one of the 10 best performances of Bonnaroo 2012.”

Fuse went a step further, gushing: “He delivered the most exciting set of the day.”

Rogers, who performs here Thursday at the Belly Up, happily recalled taking the stage at Bonnaroo last year.

“The first thing I said was: ‘Kenny Rogers and Bonnaroo? What’s wrong with this picture?” he chuckled.

“Because I felt a bit uncomfortable. At the same time, what I’ve learned is that all the people who cared about my music in my prime forced their kids to listen to it! And while I know that qualifies as child abuse, the audience at Bonnaroo knew those songs of mine...

“I was totally shocked by the degree of acceptance I got and the (favorable) reviews. I don’t think I deserved them. And I was shocked, sitting backstage with Phish, to find — in addition to ‘The Gambler’ — they knew 10 other songs of mine they offered to play. Bonnaroo was a great opportunity for me to do what I do, and then go to their stage for a song.”

How did Rogers end up at Bonnaroo in the first place? Is it because his longtime lighting director, Jeff Metter, used to work for the Grateful Dead? Guess again.

“I really prefer small venues. The thing I learned playing to 60,000 people is, you play to the first 10 rows and acknowledge the last 10. In a small venue, you play to all the rows. It’s not important to me that anyone leaves my show saying: ‘He was the best singer I’ve ever heard.’ What is important is that people say: ‘I had a really good time’.”

Now at work on his next album, Rogers doesn’t have to work to hard to give fans a good time.

The former jazz bassist — “I liked Charlie Mingus and I really loved Ray Brown’s playing in the Oscar Peterson Trio” — has 24 No. 1 singles and 12 No. 1 albums to his credit. A three-time Grammy-winner, he’s sold more than 120 million albums worldwide. Moreover, such Rogers songs as “Lucille” — which was memorably covered by the San Diego roots-rock band the Beat Farmers — have become part of the American musical fabric.

“We’re all products of our history and, in my case, I loved jazz,” Rogers noted from a recent tour stop in Virgina. “I’ve always said that I’m a country singer who’s had a lot of other musical influences. To this day, I love jazz, although some of it today is too abstract for me. My guys in my band are all jazz-capable players and play jazz in their off-time.”

Reading between the lines of his recent best-selling autobiography, “Luck or Something Like It,” Rogers seems to imply he would have been happy to continue playing jazz as a member of the Bobby Doyle Three, the Texas band in which he cut his musical teeth.

At least, he would have had he not found commercial success, first with The New Christy Minstrels, then with The First Edition and, finally, as a top-selling solo artist. Asked if that is an accurate inference, Rogers sounded, well, jazzed.

"Yeah," he said. "The great thing about success in this country is spotting opportunity and taking advantage of it. The pianist I was with, Bobby Doyle, was very avant garde, in that he wrote arrangements for a three-piece band that made it sound like there were four or five musicians . He orchestrated all the vocal parts we were going to sing. And they were very difficult, totally incongruous to what we were playing (instrumentally). At the time, it was a truly unique union of music and ability.

"I was with him for six years and then I went straight from the Bobby Doyle Three to the New Christy Minstrels, which was (doing) probably the simplest form of music I'd ever heard. What I found in folk music that I didn't find in jazz were the stories -- stories that affected people. The thing about folk music is, it really is about the people and the political side of things, and I loved that. So some of my songs, when I got into country-music, reflected that."

In his book, Rogers recounts not only his many hits (and some flops), but also his multiple marriages. In 1964, at the age of 25, he married for the third time.

“I’ve learned that I am somewhat codependent, that I’m not happy being alone and that I can commit,” said the bearded singer, who is now in the 15th year of his fifth marriage.

“I’m 74 and my body is falling apart. But I think I’m singing OK. Apart from the fact that I have 8-year-old identical twin boys, music is my purpose (in life).”

As for his legacy, Rogers is content.

“I don’t think I have anything left to prove,” he said. “The older I get, the better I used to be.”

Kenny Rogers and The Beat Farmers

Back in the 1980s, the nationally prominent San Diego roots-rock band The Beat Farmers often performed an especially memorable version of "Lucille," which in 1977 gave Rogers the first solo hit of his career. As sung by the deep-voiced Country Dick Montana, the Farmers version added some choice profanities to "Lucille's" sing-along chorus.

Asked if he was familiar with The Beat Farmers' rendition of "Lucille," Rogers paused for a moment.

"Hmm," he said. "I think someone played me their version on YouTube. Is that the one where they sing: 'You picked a fine time to leave me, Lucille -- you whore, you (female dog)'?"